Longitudinally extensive transverse myelitis (LETM) could be seen in patients with connective tissue disease (CTD), especially systemic lupus erythematosus (SLE) or primary Sjögren’s syndrome (pSS). Some patients are combined with neuromyelitis optica spectrum disorders (NMOSD)(termed CTD-LETM-NMOSD) while others without (termed CTD-LETM-non-NMOSD). The aim of this study is to compare the clinical characteristics of CTD-LETM-NMOSD patients to CTD-LETM-non-NMOSD patients. We retrospectively collected data from 40 CTD patients with LETM who were admitted to the Department of Neurology or Rheumatology at Peking Union Medical College Hospital from Jan, 2006 to Dec, 2016. They were divided into CTD-LETM-NMOSD and CTD-LETM-non-NMOSD two groups. Demographic characteristics, clinical and laboratory features were obtained from the database. Relapse rates and clinical outcome were analyzed by Kaplan-Meier method. Among 40 patients with CTD, 28 (70.0%) were NMOSD while 12 (30.0%) were not. The positivity rates of anti-SSA, antibodies to aquaporin-4 (anti-AQP4) were significantly higher in patients with NMOSD than those in patients with non-NMOSD (<0.05). Age, gender, clinical features, disease duration, anti-double-stranded DNA antibody, anti-ribosomal P antibody, antiphospholipid antibodies, expanded disability status scale (EDSS) scores, and magnetic resonance imaging (MRI) features were all comparable between two groups. CTD-NMOSD patients had significantly higher disease relapse rate (75.0% vs. 3/12, <0.01). Anti-SSA and anti-AQP4 positivity is associated with NMOSD and higher relapse rates, which suggests that NMOSD in CTD-LETM patients may represent distinct characteristics and pathogenesis from patients with CTD-LETM-non NMOSD.